Trocars of the type relating to the present invention generally include a stylet having a sharp tip for penetrating through a patient's abdominal wall or other body cavity, a protective shield tube surrounding the stylet, and an outer guide tube surrounding the protective shield tube. Typically, the protective shield tube and stylet extend beyond the distal end of the guide tube, and the protective tube is spring-biased in a locked distal position surrounding the sharp tip of the stylet. To use the trocar, the protective tube is unlocked so that the protective tube moves proximally to expose the stylet tip for penetrating the abdominal wall. Once the abdominal wall has been penetrated, the protective tube slides distally under the force of the spring to again assume the locked, distal position covering over the sharp stylet tip. In this manner the outer guide tube is placed into the body at a desired location. Thereafter, the stylet and protective tube may be removed to leave the guide tube in place. Trocars of this type are generally described in Moll U.S. Pat. Nos. 4,601,710 and 4,654,030. After the guide tube has been placed within the body, surgical instruments may be inserted through the guide tube.
Unfortunately, known trocars do not provide any indication of trocar penetration depth to the surgeon, who must estimate the penetration depth during and after penetration of the abdominal wall. Some surgeons accomplish this task by simply resting a finger on the outer guide tube as a visual aid during insertion. Of course, this approach is unreliable, since the surgeon's finger is, at best, a rough approximation of penetration depth. Moreover, the surgeon's finger is susceptible to slipping or moving during insertion of the trocar.
Numerous penetration indicating and limiting devices have heretofore been proposed in relation to various types of surgical devices and instruments. These include graduated scales or other marks, see, for example, U.S. Pat. Nos. 3,459,189 and 3,993,079, and collar-type devices with a set or fixing screw bearing against the apparatus to be inserted, see, for example, U.S. Pat. Nos. 1,213,001 and 2,496,111 and Italian Patent No. 475215. Unfortunately, in the context of a trocar, merely providing a graduated scale or mark would be inadequate since this requires conscious visual attention of the surgeon or an attendant during insertion and provides no protection against over insertion during initial penetration. Moreover, the indicia on the graduated scale or marker may become obscured under surgical conditions, and constant attention to the scale is not possible. Set or fixing screws pose the undesirable possibility that overtightening may dent or damage the device. In the case of modern trocars, such damage could impair the structural integrity of the trocar guide tube and/or interfere with the operation of instruments inserted into the body through the trocar guide tube. Even relatively minor damage to a trocar guide tube may alter the relatively small internal diameter of the tube, e.g., on the order of about 10 millimeters or less, and interfere with insertion, rotation, or operation of sophisticated medical instruments designed to operate closely within the limited trocar guide tube space.
U.S. Pat. No. 3,817,250 discloses a collar for limiting penetration of a tracheostomy device. However, that device permits penetration to only one preset depth and undesirably obscures the insertion site.
U.S. Pat. No. 3,613,684 discloses a trocar catheter having a depth penetration limiting device consisting of a slotted tubular member with a slotted, radially extending collar. In use, the limiting device is grasped to isolate the device relative to the catheter shaft during insertion. Unfortunately, it appears the depth penetrating device may slip accidentally during insertion if not grasped firmly and constantly. In addition, the device there disclosed apparently requires an inconvenient two-handed penetration technique. This would seem to require an extended trocar shaft to allow sufficient room to grasp the shaft during penetration.
Other penetration depth indicators rely upon pressure sensitive devices. These include U.S. Pat. Nos. 2,623,512; 4,186,750; and 4,215,699 and Russian Patent 921554.
Notwithstanding the foregoing disclosures, there presently exists a need for trocar penetration depth indicator which provides convenient, reliable indication of trocar penetration depth during and after one-handed insertion of a trocar, and which does not unduly lengthen the trocar guide tube or present a hazard of damaging the guide tube by overtightening a set or fixing screw.
Once penetration of the body wall has been attained, the stylet is removed, leaving a guide tube penetrating the body adapted to receive surgical instruments. However, the guide tube may be subject to unintentional and undesirable changes in penetration depth or accidental withdrawal from the body. Therefore, there also exists a need for a positioning device to hold the guide tube at the desired penetration depth during use. At the same time, however, the positioning device should accommodate manipulation of the guide tube by the surgeon during the surgical procedure.
Accordingly, it is one object of the present invention to provide a trocar depth indicator.
A further object of the present invention is to provide a trocar depth indicator which does not limit the useful penetration length of existing trocars or require undue extension of the trocar barrel length.
Another object of the present invention is to provide a trocar penetration depth indicator which may be securely positioned relative to the trocar guide tube so as to reduce the likelihood of displacement of the depth indicator along the guide tube during penetration.
It is yet a further object of the invention to provide a trocar depth indicator which may be positioned relative to the trocar guide tube without damaging the guide tube or interfering with the operation of delicate instruments inserted therethrough.
Yet another object of the present invention is to provide a trocar guide tube positioning device for positioning the inserted trocar guide tube relative to the body.
These and other objects and advantages are accomplished in a compact, lightweight and low cost device which provides reliable indication of trocar penetration depth without unduly obstructing the trocar guide tube, and which positions the inserted trocar guide tube relative to the body to prevent accidental removal of the trocar or inadvertent changes in penetration depth.